Proposed ozone standard challenges technology A computer system with the capabilities of Models-3 may be needed if EPA adopts a proposed new ozone standard. The current standard, 0.12 ppm measured in one-hour episodes, is being revisited by EPA after a 1993 lawsuit by the American Lung Association. The ALA asserts that the current standard ignores ozone's harmful cumulative effects on the lungs of children and outdoor workers. EPA is now considering resetting the standard to as low as 0.070.09 ppm and measuring in eight-hour episodes. Storing and manipulating eight hours' worth of air quality data require an enormous amount of computer memory, disk space, and speed. If EPA adopts an eight-hour standard, regulators would need a more powerful modeling system to record and simulate longer episodes. Models-3 could be the framework for that simulation, predicts John Bachmann of EPA's Office of Air Quality Planning and Standards. The Environmental Decision Support System, an early Models-3 prototype, is already proving this kind of computing to be possible. The Southeast States Air Resources Managers will use the system, running on a Cray supercomputer, to simulate the entire mid-May to mid-September ozone season, using 24-hour days. "We'll create an ozone climatology for the Southeast," said North Carolina Supercomputer Center Director of Advanced Applications Ken Galluppi. "That's never been done before because we've never had the computer power, and we've never had a system that could handle this much information." —ELAINE APPLETON
Despite the promise of "plug-and-play" hardware and software modules, Novak acknowledged that initial implementations of Models-3 will only loosely integrate model input and results. "There's no one tool that can do everything," she said. "We're trying to provide a framework that can help people access a variety of data and pull different data sets together for analysis." She hopes users will be able to run different models on such integrated data sets. In theory, that would provide better comparisons between model output than is possible with today's disparate and incompatible data sets. Practical use of Models-3 as a tool for designing and demonstrating regional control strategies depends on availability of a master database of air quality model results. EPA is working with regional and local organizations to build the database and make it available to the environmental community. NARSTO, for example, plans to contribute its own field data to the Models-3 database, said Al Farewell, a NARSTO committee chair and atmospheric scientist with Pennsylvania Power and Light in Allentown, Pa. Novak suggested that states doing their own independent modeling could share the results with, say, the Ozone Transport Commission by sending model results to the EPA's master database. The idea is to have an automated way to catalogue and make available the huge amounts of information generated by these models. Models-3 is not the only comprehensive modeling effort under way. Canada is developing such a system. So too is the Electric Power Research Institute (EPRI) with a similar effort it calls CAMRAQ (5). EPRI, based in Palo Alto, Calif., is largely funded by utilities and other regulated industries. EDSS will also be available, in some fashion, 2 0 4 A • VOL. 30, NO. 5, 1996 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
through the NCSC—probably before Models-3 is fully operational. The system currently provides three capabilities: model engineering and configuration management services; simulation planning and execution management; and analysis and threedimensional visualization (6). In the future, EDSS will include other functions such as surface and groundwater modeling; cross-media simulations of air, water, and land; economic models; and health effects models. Like Models-3, EDSS already provides urban and regional ozone models, and it will support multiscale particulate and acid deposition modeling. In June 1995, NCSC released a beta version of EDSS to pilot testers, including EPA, Cray Research, and university labs; test versions were released to state and local regulators in January. The center is offering an automated version of the Urban Airshed Model, called UAM Guides, on the World Wide Web. EDSS itself is too large to distribute via the Internet, officials said. Although new systems like Models-3 and EDSS are designed to make it easier to perform model runs, experts like Wheeler believe such ease of use could cause as many problems as it solves. "It becomes easier for someone to run the model and not necessarily be cognizant of the problems in it," he said. One solution, said NCSC officials, is to provide education as an integral part of any modeling program, a response endorsed by Wheeler. "We've learned a lot over years of experience in making mistakes, and part of the education is explaining to people what mistakes we've made and what to look for." A critical part of that educational process, he stressed, is to make users aware of degrees of uncertainty. "We know there will always be uncertainty in emissions, meteorology, model formation, et cetera," said Wheeler. "We need to tell people how much confidence they should have in a model, because the models don't make decisions, the decision makers do."
References (1) Wheeler, N.J.M. "Regional/Urban Air Quality in California, Part I: Air Quality, Simulation, and Decision Making in California"; Proceedings of the Conference on Environmental Impact Prediction: Simulation for Environmental Decision-Making, October 6-7,1994; MCNC, North Carolina Supercomputer Center: Research Triangle Park, NC, 1995. (2) Dennis, R. L. et al. Atmos. Environ. 1996, April. (3) Reichhardt, T. Environ. Sci. Technol. 1996, 30, 68A. (4) Rethinking the Ozone Problem and Urban and Regional Air Pollution; National Academy of Sciences: Washington, DC, 1991. (5) Hansen, D. A. et al. Environ. Sci. Technol. 1994, 28, 71A. (6) Ambrosiano, J. et al. Presented at EPA Next-Generation Environmental Modeling Computational Methods Workshop, Bay City, MI, Aug. 7-9, 1995. Elaine L. Appleton is a freelance science writer based in Newburypor,, Mass. She is former senior editor at Data m a t i o n magazine.
An electronic version of this article is accessible via the World Wide Web on the American Chemical Society's Publications home page (http://pubs.acs. org/hotartcl/index.html). An animation of the Models-3 screen shown on page 201A is included as a Quicklime movie and an MPEG file. —Editor
